Satellites and spacecraft don't just float randomly in space; they follow precise paths called orbits. These orbits are governed by the laws of physics, primarily gravity, and are crucial for mission success. Understanding the different types of orbits is fundamental to designing and operating space missions, from Earth observation to deep space exploration.

Before diving into specific orbit types, it's helpful to understand the parameters that define an orbit:

Orbits are categorized based on their altitude, inclination, and eccentricity, each serving different purposes.

LEO is the region closest to Earth, typically ranging from 160 to 2,000 kilometers (100 to 1,240 miles) above the surface. Satellites in LEO orbit Earth rapidly, completing a revolution in about 90 minutes. This orbit is ideal for Earth observation, reconnaissance, and the International Space Station (ISS).

MEO orbits are situated between LEO and GEO, typically between 2,000 and 35,786 kilometers (1,240 to 22,236 miles). The most common use for MEO is for navigation satellite systems, such as the Global Positioning System (GPS), Galileo, and GLONASS. Satellites in MEO have longer orbital periods than those in LEO.

GEO is a specific type of orbit located at an altitude of approximately 35,786 kilometers (22,236 miles) directly above the Earth's equator. A satellite in GEO orbits Earth at the same rate as Earth rotates, making it appear stationary from the ground. This is crucial for communication satellites, weather satellites, and broadcasting.

GSO is an orbit with an orbital period that matches Earth's rotational period. Satellites in GSO appear to return to the same position in the sky at the same sidereal time each day. While GEO is a specific type of GSO with zero inclination, other GSO orbits can be inclined, causing the satellite to trace a figure-eight pattern in the sky.

Polar orbits have a high inclination, typically close to 90 degrees. As the Earth rotates beneath the satellite, a polar-orbiting satellite can observe virtually the entire surface of the planet over time. These orbits are commonly used for Earth mapping, reconnaissance, and environmental monitoring.

An SSO is a special type of near-polar orbit where the satellite passes over any given point of the Earth's surface at the same local solar time. This is achieved by carefully selecting the orbit's inclination and altitude. SSOs are highly valuable for remote sensing and imaging satellites, as they provide consistent lighting conditions for repeated observations.

Elliptical orbits are characterized by an eccentricity greater than zero. They have a perigee (closest point to Earth) and an apogee (farthest point from Earth). Highly elliptical orbits (HEO) are used for specific purposes, such as providing coverage to high-latitude regions or for scientific missions that require extended periods of observation at a particular distance.

The selection of an orbit is a critical design decision in space missions, directly impacting the satellite's capabilities, mission duration, and operational costs. Factors such as the desired coverage area, communication needs, scientific objectives, and the celestial body being orbited all play a role.